When is light pollution relevant to planning?

Artificial light provides valuable benefits to society, including through extending opportunities for sport and recreation, and can be essential to a new development. Equally, artificial light is not always necessary, has the potential to become what is termed ‘light pollution’ or ‘obtrusive light’ and not all modern lighting is suitable in all locations. It can be a source of annoyance to people, harmful to wildlife, undermine enjoyment of the countryside or detract from enjoyment of the night sky. For maximum benefit, the best use of artificial light is about getting the right light, in the right place and providing light at the right time.

What factors should be considered when assessing whether a development proposal might have implications for light pollution?

Some proposals for new development, but not all, may have implications for light pollution. The following questions will help to identify when the possibility of light pollution might arise:

Does a new development proposal, or a major change to an existing one, materially alter light levels outside the development and/or have the potential to adversely affect the use or enjoyment of nearby buildings or open spaces?

Does an existing lighting installation make the proposed location for a development unsuitable? For example, this might be because:

the artificial light has a significant effect on the locality;

users of the proposed development (eg a hospital) may be particularly sensitive to light intrusion from the existing light source.

Does a proposal have a significant impact on a protected site or species eg located on, or adjacent to, a designated European site or where there are designated European protected species that may be affected?

Is the development in or near a protected area of dark sky or an intrinsically dark landscape where it may be desirable to minimise new light sources?

Are forms of artificial light with a potentially high impact on wildlife (eg white or ultraviolet light) being proposed close to sensitive wildlife receptors or areas, including where the light shines on water?

Does the proposed development include smooth, reflective building materials, including large horizontal expanses of glass, particularly near water bodies (because it may change natural light, creating polarised light pollution that can affect wildlife behaviour)?

If the answer to any of the above questions is ‘yes’, local planning authorities and applicants should think about:

What factors are relevant when considering where light shines?

Light intrusion occurs when the light ‘spills’ beyond the boundary of the area being lit. For example, light spill can impair sleeping, cause annoyance to people, compromise an existing dark landscape and/or affect natural systems (eg plants, animals, insects, aquatic life). It can usually be completely avoided with careful lamp design selection and positioning:

Lighting near or above the horizontal is usually to be avoided to reduce glare and sky glow (the brightening of the night sky).

Good design, correct installation and ongoing maintenance are essential to the effectiveness of lighting schemes.

Common causes of complaints to local authorities are about domestic, shop or office exterior security lights, illuminated advertising and flood lighting, so these installations may require particular attention.

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What factors are relevant when considering when light shines?

Lighting only when the light is required can have a number of benefits, including minimising light pollution, reducing harm to wildlife and improving people’s ability to enjoy the night-sky:

Lighting schemes could be turned off when not needed (‘part-night lighting’) to reduce any potential adverse effects eg when a business is closed or, in outdoor areas, switching-off at quiet times between midnight and 5am or 6am. Planning conditions could potentially require this.

Impact on sensitive wildlife receptors throughout the year, or at particular times (eg on migration routes), may be mitigated by the design of the lighting or by turning it off or down at sensitive times.

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What factors are relevant when considering how much the light shines?

Considering how much light shines includes an assessment of the quantitative and spectral attributes of the lighting scheme (eg light source and performance levels) and whether it exceeds the levels required to fulfil its intended purpose. The character of the area and the surrounding environment may affect what will be considered an appropriate level of lighting for a development. In particular, lighting schemes for developments in protected areas of dark sky or intrinsically dark landscapes should be carefully assessed as to their necessity and degree.

Glare should be avoided, particularly for safety reasons. This is the uncomfortable brightness of a light source due to the excessive contrast between bright and dark areas in the field of view. Consequently, the perceived glare depends on the brightness of the background against which it is viewed. It is affected by the quantity and directional attributes of the source. Where appropriate, lighting schemes could include ‘dimming’ to lower the level of lighting (eg during periods of reduced use of an area, when higher lighting levels are not needed).

More lighting does not necessarily mean better lighting. For example, large differences in adjacent lit areas can mask activity in shadow and cause areas of high contrast or glare.

White light, with more blue content or with ultraviolet content, is generally more disruptive to wildlife than, say, yellow/orange light. Similarly, for humans, light intrusion by white/blue light is more disruptive to sleep. Use of newer white light sources that filter out blue or ultraviolet light may mitigate these effects, as well as offering superior directional control. However, whiter light aids people’s vision and ability to perceive colour; it also facilitates CCTV use.

The needs of particular individuals or groups should be considered where appropriate (eg the safety of pedestrians and cyclists). Schemes designed for those more likely to be older or visually impaired may require higher levels of light and enhanced contrast, together with more control, as the negative effects of glare also increase with age.

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What factors are relevant when considering possible ecological impact?

Wildlife differ from humans in their sensitivity to light (eg they can be affected by very low levels of light) and may be adversely affected in a number of ways (see the Royal Commission on Environmental Pollution’s 2009 report, Artificial light in the environment). The positioning, duration, type of light source and level of lighting are all factors that can affect the impact of light on wildlife.

The ability of some building materials to polarise light may cause insects, birds and other wildlife to mistake the material for water. This is a daytime and night-time effect and is different to artificial light reflected off surfaces. The effect is particularly strong with smooth (shiny) dark surfaces and may be important to consider when assessing schemes near water bodies. The use of rough, matt, light-coloured materials may reduce the effect.

Further advice is available from the Defra and Natural England websites on handling the impact on wildlife – including from artificial light – where European protected sites or European protected species could be affected. The specific nature of any consideration will depend on the features of any protected site or presence of any protected species.

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